How to Lie with Statistics

If the source of your information gives you also the degree of significance, you’ll have a better idea of where you stand. This degree of significance is most simply expressed as a probability,

It is the illusion of the shifting base that accounts for the trickiness of adding discounts. When a hardware jobber offers “50% and 20% off list,” he doesn’t mean a seventy percent discount. The cut is sixty percent since the twenty percent is figured on the smaller base left after taking off fifty percent.

This book is a sort of primer in ways to use statistics to deceive. It may seem altogether too much like a manual for swindlers.

The fallacy is an ancient one that, however, has a powerful tendency to crop up in statistical material, where it is disguised by a welter of impressive figures. It is the one that says that if B follows A, then A has caused B.

More people were killed by airplanes last year than in 1910. Therefore modern planes are more dangerous? Nonsense. There are hundreds of times more people flying now, that’s all.

Not all the statistical information that you may come upon can be tested with the sureness of chemical analysis or of what goes on in an assayer’s laboratory. But you can prod the stuff with five simple questions, and by finding the answers avoid learning a remarkable lot that isn’t so. Who Says So?

The test of the random sample is this: Does every name or thing in the whole group have an equal chance to be in the sample? The purely random sample is the only kind that can be examined with entire confidence by means of statistical theory, but there is one thing wrong with it. It is so difficult and expensive to obtain for many uses that sheer c

Author Louis Bromfield is said to have a stock reply to critical correspondents when his mail becomes too heavy for individual attention. Without conceding anything and without encouraging further correspondence, it still satisfies almost everyone. The key sentence: “There may be something in what you say.”

When you are told that something is an average you still don’t know very much about it unless you can find out which of the common kinds of average it is—mean, median, or mode.